CRACK THEORY: Spamton's valentines letters take place after ch3+4 where he is trying to reach Tenna via spam emails that he sent out to random computers in Hometown
Based on the tone of the letters, they're significantly different from how Tenna is brought up in the sweepstakes. The "damn you tenna" page has the tone of hostility and deep resentment. While these letters feel like they come from a sense of confusion(?) and just pettiness.
>THEY'RE DROWNING ME IN [Insulating foam] letter
Pipis are technically food, Tenna keeping it means he still holds Spamton in his [MansHeart].
Spamton is demanding answers for why Tenna clearly misses him but isn't letting him back into his life. It doesn't make any sense to him.
>WHY DID YOU CHANGE YOUR [credit card number] letter
Spamton trying to reach Tenna through his credit card number(or one from the light world) except it expired/got changed. He could also be asking why Tenna changed owners without telling him.
"I thought we had [kids]! I thought we had a [set]!" is Spamton echoing Tenna's "Mike! Rebuild my set! Rebuild my kids!" line back to him.
>LOVE-LETTER-FOR-YOU.TXT .vbs
Spamton sends a fucking virus to Mettaton's computer. This is his last resort.